1. Field of the Invention
The present invention relates to a semiconductor device. More specifically, the present invention relates to a semiconductor device of chip on board (COB) type with a plurality of semiconductor elements mounted on a printed wiring board.
2. Prior Art
A conventional semiconductor manufacturing method with a plurality of semiconductor elements mounted will be described in reference to FIG. 9. A first semiconductor element 601 is adhered to a predetermined location on a printed wiring board 606 with a die bonding material 603, as shown in FIG. 9. Then a second semiconductor element 602 smaller than that of the first semiconductor element 601 is similarly adhered to a predetermined location with a die bonding material 608.
Next, a wiring pattern 605 provided on the printed wiring board 606 and the semiconductor element 601 are electrically connected to each other via a thin wire for connection (Au wire, Al wire and the like) 604. Then the wiring pattern 605 and the semiconductor element 602 are electrically connected to each other via a thin wire for connection (Au wire, Al wire and the like) 609.
After that, resin sealing is achieved by an epoxy resin 607 to protect the first semiconductor element 601, the second semiconductor element 602 and the thin wires for connection 604 and 609. Thereby the semiconductor device is completed.
In the above conventional method however, the smaller the second semiconductor element becomes, the longer the thin wire for connection becomes. For this reason, the problem arises that the shape of the thin wire for connection changes to short with the adjacent thin wire for connection. As a result, the reliability of the semiconductor device becomes reduced.
The object of the present invention is to provide a novel and improved semiconductor device on which a plurality of semiconductor element can be mounted without reducing the reliability of the semiconductor device.
In the typical present invention to achieve the above object, there is provided a semiconductor device comprising: a printed wiring board with a wiring pattern; a first semiconductor element mounted on a predetermined location on the printed wiring board and having a plane with a first region in which an electrode pad is formed and a second region, the internal region of the first region; an auxiliary member mounted on the second region of the first semiconductor element and having a plane with a first region in which a wiring pattern is formed and a second region, the internal region of the first region; and a second semiconductor element mounted on the second region of the auxiliary member and having a plane with an electrode pad formed; and wherein: the electrode pad of the first semiconductor element and the wiring pattern of the printed wiring board are electrically connected to each other; the electrode pad of the second semiconductor element and the wiring pattern of the auxiliary member are electrically connected to each other; the wiring pattern of the auxiliary member and the wiring pattern of the printed wiring board are electrically connected to each other; and the first semiconductor element and the second semiconductor element are resin-sealed.
In the above-described invention, since the first and second semiconductor elements are connected by a thin wire for connection to each other, the length of the thin wire for connection can be shorter than the conventional one. As a result, even if a smaller second semiconductor element is mounted, the shape of the thin wire for connection does not change and the thin wire for connection can be prevented from shorting with the adjacent thin wire for connection, so that the semiconductor device with high reliability can be provided.